1. Field of the Invention
The present invention relates to a lubricant applying unit, a process cartridge including the lubricant applying unit, and an image forming apparatus provided with the process cartridge including the lubricant applying unit. More particularly, the present invention relates to a lubricant applying unit that applies a lubricant on a surface of an image bearing member and forms a thin layer of the lubricant, a process cartridge that includes the above-described lubricant applying unit, and an image forming apparatus that is provided with the process cartridge having the lubricant applying unit therein.
2. Discussion of the Related Art
Related art electrophotographic image forming apparatuses generally use a photoconductive method to form an electrostatic latent image on a surface of an image bearing member. An electrostatic force then adheres fine particles of toner and develops the electrostatic latent image to a visible toner image. Such related art image forming apparatuses that employ an electrophotographic image forming method generally include a lubricant applying unit that applies a lubricant on the surface of the image bearing member.
In a related art image forming apparatus, the lubricant applying unit may be used to eliminate problems that may be caused during a cleaning process. For example, the lubricant applying unit may solve problems when a cleaning brush or a cleaning blade remove residual toner remaining on the surface of the image bearing member after an image transferring operation has been performed. Specifically, the lives of an image bearing member and an intermediate transfer belt mainly depend on a degree of wear caused during the process in which the image bearing member and the intermediate transfer belt are in mechanical contact in a sliding manner with a cleaning brush or a cleaning blade of the image forming apparatus. Therefore, an operation of applying a lubricant on the respective surfaces of the image bearing member and the intermediate transfer belt can reduce a friction coefficient of the respective surfaces thereof and prevent the wear of the image bearing member and the intermediate transfer belt. Thus, the image bearing member and the intermediate transfer belt can obtain longer lives.
When the surface of the image bearing member is coated with a lubricant, the life of the image bearing member may become longer. In addition, as a friction coefficient of the surface of the image bearing member is reduced, foreign materials that are adhered to the surface of the image bearing member may easily be removed. That is, the application of the lubricant onto the surface of the image bearing member enables a cleaning brush or a cleaning blade to easily remove residual toner remaining on the surfaces of the image bearing member or of the intermediate transfer belt even after the transfer process has been completed.
Recently, substantially spherical toner manufactured by a polymerization method is commonly used for image forming. The substantially spherical toner can achieve a constant particle size distribution and a smaller spherical toner effectively, which can increase a level of image quality.
On the contrary, it is difficult to remove the substantially spherical toner adhered or remaining on the surface of the image bearing member.
From the above-described point of view, it may be important to employ a lubricant applying unit for applying a lubricant on a surface of an image bearing member to enhance a cleaning ability with respect to the surface of the image bearing member.
Generally, a solid lubricant may be applied to a surface of an image bearing member by a small amount in a powder form. By now, various techniques have been proposed to obtain better performance in the application of a lubricant as follows:
(1) A brush-type lubricant applying member rotates and scrapes a block-type solid lubricant so that the scraped lubricant in a powder form can be applied to the surface of the image bearing member.
(2) A lubricant is externally added to a toner particle. In this case, the amount of lubricant to be applied to the photoconductor may vary according to an image area to be output, and it is difficult to constantly apply a stable amount of lubricant for the entire surface of the image bearing member. Therefore, it is preferable to use a brush-type lubricant applying member to evenly apply a constant amount of lubricant to the entire surface of the image bearing member.
The above-described two techniques require a unit for applying a lubricant to an image bearing member. To maximize wear prevention and increase cleaning ability when the lubricant is applied to a surface of an image bearing member, it is important to control the amount and condition of the application of the lubricant. If a user wishes to enhance a lubricant's lubricating ability, the lubricant may be applied by an amount greater than a predetermined amount. However, an excess amount of lubricant may overflow and run out to adjacent units. For example, when an excess amount of lubricant enters into a charging unit, the amount of toner charge cannot properly be controlled. In addition, since recent image forming apparatuses and printers are becoming smaller in size, the elements and parts used therein are also required to be made smaller. Therefore, it is not desirable that an unnecessarily large-sized solid lubricant is provided to the small-sized image forming apparatuses and printers.
(3) A temperature of a surface of an image bearing member controls a pressure force of a solid lubricant with respect to the image bearing member and a rotation speed of a lubricant applying brush contacting the solid lubricant.
(4) An amount of a lubricant applied per rotary driving distance of the photoconductor is regulated.
(5) A number of rotations of a lubricant applying brush is controlled on the basis of image forming data.
(6) A user can avoid repurchasing an image forming apparatus when the user wishes to change the performance of the image forming apparatus. A plurality of types of engine units with different performance capabilities are respectively provided with nonvolatile memory units. The engine units in the image forming apparatus can be replaced. The image forming apparatus includes a control unit therein, by which the performance of the entire image forming apparatus is controlled on the basis of the information of the memory units in the installed engine units. This permits modifying the performance of the entire image forming apparatus, which relates to the recording rate and resolution or the like, simply by replacing the engine units with engine units that have different performance capabilities, even in the common image formation apparatus. The versatile and diversified types of machines can easily be handled.
(7) A lubricant applying unit that can ensure the control and uniformity of application quantity of the lubricant applied on a surface of a photoconductor is provided in a related art image forming apparatus. The lubricant applying unit includes a cleaning unit with a rotatable brush roller that is held in contact with a rotating image bearing member and applies a lubricant on the surface of the image bearing member, and a lubricant applying member that can be held in contact with or be separated from the rotatable brush roller. The lubricant is divided into a plurality of parts in a longitudinal direction thereof, and each of the parts can be held in contact with and can be separated from the rotatable brush roller.
(8) A proper amount of lubricant is economically applied to a surface of an image bearing member. In a related art image forming apparatus, a lubricant applying unit employing this technique includes a lubricant supplying part that is formed of a rotatable lubricant member and a lubricant, and a lubricant coating member that is rotated to coat the surface of the image bearing member with the supplied lubricant.
(9) Uneven coating caused by the tilt of the bristles of a lubricant applying brush is prevented by adjusting a pressuring force to the lubricant applying brush. A different related art image forming apparatus includes a lubricant applying member for applying a solid lubricant to a drum-shaped image bearing member that is equipped with a fur brush arranged between the drum-shaped image bearing member and the solid lubricant, so that the fur brush can scrape the solid lubricant to apply the scraped powder lubricant to a surface of the drum-shaped image bearing member, a pressuring member that is mounted on a lubricant case and includes a spring for pressing and energizing the solid lubricant to the fur brush, and a pressuring force changing means that is mounted on the lubricant case and previously includes a plurality of locations opposite to the solid lubricant to sandwich the spring so that the pressuring force of the spring can be changed by adjusting the plurality of locations.
However, the various techniques described above have not provided any technical thoughts to improve defects of a sliding performance between a lubricant supporting member, which supports a solid lubricant in a lubricant applying unit, and an internal surface of a lubricant holder, which accommodates the lubricant supporting member. This causes the solid lubricant to unevenly be pressed to a lubricant applying brush, which can easily cause variation in an amount of lubricant to be applied to a surface of an image bearing member.
Further, when an excess amount of lubricant is applied to the surface of the image bearing member, adjacent units such as a charging unit may easily be contaminated. On the contrary, when a smaller amount of lubricant is applied to the surface of the image bearing member, filming in which residual toner adheres to the surface of the image bearing member can easily be caused.